Internal cooling for turbine vanes

ABSTRACT

A structure for internally cooling an airfoil vane in an axial flow gas turbine. The vane defines a cavity which approximates the shape of the outer airfoil. A frame of similar shape is inserted into the cavity in spaced relation therefrom. The cavity walls and the frame cooperatively define a cooling passageway. A row of oblong apertures is disposed along the leading edge of the frame and a second row of apertures is disposed along the convex side of the frame, the second row of apertures being inclined relative to the cavity wall. Pressurized cooling air enters the frame, is forced through the apertures, impinges against the inner walls of the vane, and flows along the passageway to cool the vane.

United States Patent [191 Durgin et al.

[451 Oct. 23, 1973 INTERNAL COOLING FOR TURBINE VANES [73] Assignee:Westinghouse Electric Corporation,

Pittsburgh, Pa.

22 Filed: July 30,1971

21 Appl. No.: 167,586

[52] U.S. Cl. 416/97, 415/115 [51] Int. Cl. F01d 5/08 [58] Field ofSearch 416/96, 96 A, 97, 416/90, 95; 415/115 [56] References CitedUNITED STATES PATENTS 2,873,944 2/1959 Wiese et a1. 416/97 UX 3,032,3145/1962 David 416/90 3,388,888 6/1968 Kercher et al. 415/115 3,475,10710/1969 Auxier 415/115 3,623,318 11/1971 Shank 415/115 FOREIGN PATENTSOR APPLICATIONS 1,222,565 2/1971 Great Britain 416/97 PrimaryExaminer-Everette A. Powell, Jr. Attorney'A. T. Stratton et al.

[57] ABSTRACT A structure for internally cooling an airfoil vane in anaxial flow gas turbine. The vane defines a cavity which approximates theshape of the outer airfoil. A frame of similar shape is inserted intothe cavity in spaced relation therefrom. The cavity walls and the framecooperatively define a cooling passageway. A row of oblong apertures isdisposed along the leading edge of the frame and a second row ofapertures is disposed along the convex side of the frame, the second rowof apertures being inclined relative to the cavity wall. Pressurizedcooling air enters the frame, is forced through the apertures, impingesagainst the inner walls of the vane, and flows along the passageway tocool the vane.

4 Claims, 6 Drawing Figures PATENIEBOU23 ma 3.767.322 sum 10F a FIG. I

INVENTORS WITNESSES J George A.Durg|n 8 L ZW/w'V'JQ/QZW Philip S.Bornobei INTERNAL COOLING FOR TURBINE VANES BACKGROUND OF THE INVENTIONThe following relates to stationary blades or vanes in an axial flow gasturbine and more specifically to means for cooling the vanes.

As is well known in the art, one of the limiting factors in gas turbinedesign is the ability of the blades to withstand high gas turbinetemperatures, particularly in the first and second stages of theturbine. One cooling vane structure is shown in J.A. Pyne, .Ir., U.S.Pat. No. 3,574,481, patented Apr. 13, 1971. A similar type of vanecooling structure is disclosed in Gabriel application Ser. No. 43,533,filed June 4, 1970, now abandoned, and assigned to the present assignee.

One problem area of cooling turbine vanes is to direct the cooling fluidto localized high heat flux portions of the vane and to uniformly coolthe vanes. A second problem area is to maximize the effectiveness of thecooling fluid by metering and channeling the cooling fluid along thevanes internal surfaces and preventing excessive cross flow of fluidfrom one side of the vane to the other.

Another problem is that there is a close tolerance requirement inpositioning the frame within the vane cavity and therefore the closetolerances increase the cost of the blade.

It would be desirable then to devise a cooling system for a turbine vanewhich effectively directs the cooling fluid to the localized high heatflux portions of the vane, which system would more effectively cool thevane, and which system would easily position the insertable frame withinthe vane allowing for increased tolerances. I

SUMMARY OF THE INVENTION A cooling system for a turbine vane, the vanedefining a cavity therein. The cooling system includes a hollow framestructure of generally airfoil shape, which is disposed within thecavity and is spaced therefrom. The wall of the cavity and the framecooperatively define a cooling passageway of general airfoil shape. Arow of apertures is disposed along the leading edge of the frame andcooling air is forced into the frame, through the, apertures andimpinges on the leading edge of the internal wall of the vane. Afterimpingement, the coolin g air divides in the passageway, one halfflowing along the passageway on the convex (or Higher Heat Flux) side ofthe vane, and the other half flowing along the passageway on the concaveor lower heat flux side of the vane.

A second row of apertures is disposed on the convex side of the frame,downstream of the leading edge. The apertures are inclined relative tothe internal wall of the vane. A third row of apertures may be disposedfurther downstream of the second row of apertures in the frame, theapertures also being inclined relative to the internal wall of the vane.In both, the second and third rows of apertures, cooling air within the.frame is forced out through the apertures on the leading edge of theframe and impinges upon the internal wall of the vane. The cooling airimpinging upon the side wall of the vane at a predetermined angle,thereby more effectively. cools the localized high heat. flux portion ofthe vane by direct impingement of metered coolant fromv within theframe.

- An expandible seal structure is secured to the trailing edge of theframe with a plurality of apertures extending along the radial height ofthe seal structure. The apertures in the seal structure are designed tometer the coolant flowing along the concave surface of the vane and inturn equalize the static pressures on both sides of the apertures at theleading edge of the frame. Equalization of the static pressures at theframe leading edge will prevent deflection of the impinging jets offluid and thereby prevents a maldistribution of cooling fluid betweenthe concave and convex vane surfaces.

The expandible seal structure is made resilient so that the seal surfaceconforms to the cavity irregularities along the full height of the sealand thereby providing accurate metering of the coolant fluid through theapertures in the seal structure. The expandible seal structure alsolocates the frame within the vane cavity in such a manner as to provideaccurate positioning of the frame to the convex surface of the vaneallowing for increased vane cavity tolerances while maintaining coolinguniformity.

What is disclosed, then, is a cooling system for a hollow turbine vane,the cooling system distributing the cooling fluid to the localized highheat flow portions of the turbine vane to more uniformly cool the vane.Furthermore, the cooling system meters the cooling fluid and preventsexcessive crossflow from one side of the vane to the other. Finally, thecooling system provides a frame insertable into the cavity in the vanewhich increases the tolerances between the frame and the cavity in thevane.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a partial axial sectionalview of a gas turbine having vane structures incorporating the inventiontherein.

FIG. 2 is an enlarged isometric view partly in section of one vanestructure shown in FIG. 1.

FIG. 3 shows an enlarged view taken along line III- -III in FIG. 1.

FIG. 4 shows an enlarged view along line FIG. 1.

FIG. 5 is an enlarged view taken along line VV in FIG. 1; and

FIG. 6 is an enlarged sectional view taken along line VI-VI in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings indetail, and particularly in FIG. 1, there is shown a portion of an axialflow gas turbine having a rotor structure 10 and an inner casingstructure 11. The rotor structure 10 is rotatably supported within thecasing structure 11 in a manner well known in the art. At least oneannular row of rotating blades 13 extend radially outward from the rotor10. Cooperatively associated with the rotating blades is an annular rowof stationary blades or vanes 15 which are supported from the casing 11and project radially inwardly. The first row of rotating blades 13 andthe first row of stationary blades l5'define the first turbine stage 17.A second row of stationary blades or vanes 19 is also shown, the secondrow having a larger area to expandthe hot motor fluid, as indicated bythe arrows 20, from left to right and as well known in the art.

The hot motor fluid, such as pressurized combustion gas, is generated ina plurality of circumferentially dis- IVIV in posed combustion chambers(not shown). The gases flow pass the stationary blades 15 and 19 and therotary blades 13 with resulting expansion of the gases to rotate therotor about its rotational axis R-R. Each stationary blade has aradially inner shroud 21 and a radially outer shroud platform 22. Theplatform 22 has axially extending projections 24a and 24b which extendinto corresponding grooves 26a and b in the casing structure 11 tosecure the vanes 15 within the casing structure. The radially outersurface of the platform 22 and the casing structure 11 jointly define acontinuous annular inner plenum chamber 28. A hollow tubular insert 30is disposed in the casing structure 11 to provide fluid communicationbetween an outer plenum chamber 31 and the inner plenum chamber 28.

An annular seal housing structure 32-is disposed on the radially innerside of the stationary blades 15. An annular seal structure 33 isdisposed in an annular groove 34 within the housing structure 32 and isspring biased therein by spring 36 to urge the seal structure 33 intofrictional abutment with the radially inner surface of the inner shroud21. The seal structure 33 and shroud 21 cooperatively prevent leakage ofthe hot motive fluid, as represented by the arrows 20, from leakingaround the stationary blades 15.

An annular segmented sealing member 38 is disposed I within the casingstructure 11. A tubular insert 40 is disposed within the casingstructure 11 and is spring biased to maintain the sealing member inproper position. The sealing member 38 and the casing structure definean annular cavity 41, the insert 40 providing fluid communicationbetween the outer plenum chamber 31 and cavity 41.

Immediately downstream of the first stage 17 is the second row ofstationary blades 19. The blades 19 are disposed within the casing 11 ina similar manner to that described for the first row of stationaryblades 15. Each stationary blade 19 has a radially outer shroud orplatform 43 and a radially inner shroud 44. The radially outer shroud 43and the inner casing structure 11 jointly define a plenum chamber 46. Atubular hollow insert 48 is disposed within the casing 11 and providesfluid communication between the outer plenum chamber 31 and the plenumchamber 46.

An annular projection 50 extends radially inward from the inner shroud44 and cooperates with an axial projection 51 on the rotor structure 10to provide a partial seal between the first stage 17 and the secondstationary row of blades 19. An expandible seal structure 53 cooperateswith a radially extending portion 54 of the vane 19 and the rotor 10 toeffectively seal between the second row of vanes 19 and the secondrotating row of blades (not shown). The seal structure 53 includes alabyrinth type of seal 55.

In accordance with the principles of the present invention, there isprovided a cooling system for the turbine vanes 15 and 19. As seen inFIGS. 2, 3, 4 and 5 each turbine vane 15 is of general airfoilcross-section and defines a cavity 57. A hollow frame structure 58 isdisposed within the cavity 57. The frame structure 58 is also of airfoilcross-section and is slightly smaller in size and similar in shape tothe vane 15.

The internal wall 60 of the vane 15 and the external wall of the frame58 cooperatively define a cooling passageway 61 of general airfoilcross-section. The passageway 61 extends along the radial height of thevane.

The vane 15 has a leading edge 62 (FIG. 3) and a trailing edge 63, theedges being connected by a convex side wall 65 and a concave side wall66. Correspondingly, the frame 58 has a leading edge 67 and a trailingedge 68, the edges being connected by a generally convex side wall 70and a generally concave side wall 71.

On the leading edge 67 of the frame 58 is a plurality of apertures 73disposed along the radial height of the frame. The apertures 73 as shownare oblong in shape and have a longer radial height a than width b (FIG.2). Apertures 73 provide fluid communication between the inside of theframe 58 and the airfoil passageway 61.

On the convex side wall 65 is a first indented wall portion 75 (FIGS. 2and 3). A plurality of circular apertures 76 are disposed along theradial height of the frame 58 on the indented wall portion 75 of theconvex side wall 70. The apertures 76 are inclined at an acute anglerelative to the internal vane wall 60.

Downstream of the indented wall portion 75 is a second indented wallportion 78. A plurality of circular apertures 79 are disposed along theradial height of the indented wall portion and are inclined at an acuteangle relative to the internal vane wall 60.

At the trailing edge 68 of the frame 58 is an expandible seal structure81 (FIGS. 2. and 3). The expandible seal structure 81 can be an integralpart of the frame 58 and extends further downstream into the passageway61. The seal structure 81 is hook shaped and extends along the entireradial height of the frame. A plurality of apertures 83 are disposedalong the radial height of the seal at spaced intervals and providefluid communication between the convex side and the concave side of thepassageway 61. The expandible seal structure is made resilient to assistin properly positioning the frame 58 within the cavity 57 and to provideuniform sealing along the radial height of the seal surface, resultingin uniform metering of cooling flow through circular apertures 83.Mixing of uniformly metered flow from the convex and concave side ofpassageway 61 provides a regulated supply of cooling fluid flowingthrough the exit cooling passageways 84 which are disposed along thetrailing edge 63 of the vane 15.

On the radially inner portion of the frame 58 is an end plate sealingmember 85 of airfoil shape which prevents cooling fluid communicationbetween passageway 61 and the area inside of the frame 58 at theradially inner portion of the frame. As best seen in FIGS. 2 and 4,sealing plate 87, also of airfoil shape prevents fluid communicationbetween passageway 61 and the hot motive fluid 20 through the innershroud 21 of vanes 15.

On the convex side wall 65, there is disposed a plurality of dimple-likestructures 88, which structures are positioned immediately upstream ofthe indented wall portion 75. The dimple-like structures 88 assist toproperly position the frame 58 within the cavity 57.

On the convex side wall 70 of the frame is also disposed a series ofpositioning structures 89 (FIG. 3) to assist in properly positioning theframe. On the concave side wall 71 of the frame 58 is a series of threepositioning structures 90, as best seen in FIGS. 2 and 4. The radiallyouter portion 91 of the frame 58 is secured to the radially outer shroud22 of the vane 15 (FIG. 4).

The second row of vanes 19 are similar to the first row of vanes 15except for the following. The second row of vanes 19 increase in radialheight in a downstream direction from the leading edge 93 to thetrailing edge 95 (FIGS. 1 and 5). A hollow frame 97 of general airfoilcross-section is disposed within the vane 19 and is in spaced relationtherewith. The frame 97 has a leading edge 100 and a trailing edge 101,the edges being connected by a convex side wall 103 and a concave sidewall 104. A plurality of apertures 106 are disposed along the radialheight on the leading edge 100 of the frame 97. On the convex side wall103 is an indented portion 108 on which is disposed a plurality ofapertures 110, the apertures being disposed along the entire radialheight thereof. The apertures are inclined relative to the internal wallof the vane 19.

A plurality of dimple like projections protrude from the convex sidewall 103 immediately upstream of the indented wall portion 108. Thelocal dimple like protrusions 112 are positioned along the radial heightof the frame 97 and assist in properly positioning the frame from theinternal wall of the vane 19.

Downstream of the indented wall portion 108 are positioning structures114 which project outwardly from the convex side wall 103 of the frame97.

On the concave side wall 104 are a plurality of positioning structures116. At the trailing edge 101 of the frame 97 is an expandible sealstructure 118 having a plurality of apertures 119 disposed along itsradial height and providing fluid communication between the convex andconcave side of the fluid flow passageway.

There are a plurality of air exit apertures 121 along the vane concaveside upstream of the trailing edge 95 providing fluid communicationbetween the hollow vane 19 and the external surface of vane 19, whichdirects the hot motive fluid 20.

An insertible closure member 123-is disposed in the radially innerportion of the vane 19 and has a plurality of hollow tubular members 125disposed radially therein to provide fluid communication between thecavity defined within the frame 103 and the seal structure 53 (FIG. 1).

In operation, pressurized air from the outer plenum chamber 31 (FIG. 1)flows through the tubular inserts 30 and 48 as indicated by the arrows Band flows into the inner plenum chambers 28 and 46. From the plenumchambers 28 and 46 the pressurized cooling air then flows into the vanesand 19 as indicatd by the arrows C.

Pressurized air C is forced through the oblong apertures 73 andperpendicularly strikes the internal wall of the leading edge 62 (FIG.3), to provide direct impingement cooling of the leading edge. Theapertures 73 are oblong rather than circular in shape since for acomparable aperture area, the cooling air can be more accuratelydirected to the internal wall of the. leading edge 62 of the vane.Furthermore, by using oblong apertures, more uniform cooling can beachieved at the leading edge then if circular apertures were used sincethe width B of the apertures is substantially uniform and closely spacedalong the radial height of the leading edge 67 of the frame 58. The useof circular apertures requires a greater number of apertures havinglarger radial spacings and increased widths b (i.e., diameters) for anequivalent cooling flow area when compared to the oblong apertures.These increased widths and larger radial spacings between apertures cancause nonuniformity in leading edge cooling with the existence ofvariations in aperture location and vane side-to-side static pressuregradients.

After impinging upon the internal wall of the leading edge 62 of thevane 15, the cooling air divides as indicated by the arrows D in FIGS. 2and 3, one portion flowing in the passageway 61 to impinge andconvectively cool the internal wall on the convex side wall 65 of thevane and the other portion to impinge and convectively cool the internalwall on the concave side wall 66 of the vane.

Pressurized cooling air is also ejected through the circular apertures76 in the indented wall portion of the frame 58. As previouslymentioned, the convex wall portion 65 of the vane has a higher heat fluxthan the concave portion 66. Therefore, additional cooling air isinjected through the apertures 76 into the passageway 61 as indicated bythe arrows E to directly impinge upon the internal wall of the convexside wall 65 and to provide additional impingement and convectivecooling locally along passageway 61. The apertures 76 are circular inshape for better penetration through the partially spent cooling airfrom the apertures 73.

Furthermore, for a given cooling requirement there is a range ofparticular circular hole sizes, centerline spacings in the radialdirection, and hole inclination to the vane inner surface for thecross-flow of partially spent coolant which must be penetrated. Theapertures are inclined relative to the internal wall portion of thevane, the greater the inclinationof the apertures the greater thesurface coverage, however, the localized cooling effect is reduced. Theapertures 76 are positioned at a location where the coolingeffectiveness of the air from the apertures 73 is diminished and a highcooling requirement exists.

In the first row of vanes 15 because of the high temperatures and highheat flux therein, further cooling of the convex side wall 65 of thevane is desirable. Correspondingly, cooling air is projected through theapertures 79 as indicated by the arrows F for direct impingement of thecooling air upon the internal side wall of the vane. The apertures 79are located where the cooling effectiveness of the air from theapertures 73 and 76 is substantially reduced. As with apertures 76,apertures 79 are inclined relative to the internal wall of the convexside 65 for the reasons previously cited.

The expandible seal structure 81 in FIG. 3, and the seal structure 118in FIG. 5 assist to properly position the insertible frames 58 and 97into each corresponding vane. The seal structure is made resilient whichallows more flexibility of the frame and enables the more expensive vaneportion to be made with lower tolerances. An additional function of theseal structures 81 and 118 is that in cooperation with the apertures.

The seal structure allows for cooling fluid metering through apertures83 and 119 and likewise pressurizes the coolant passageway on theconcave side 71 and 104 such that the static pressures on each side ofthe leading edge apertures 73 and 106 are equalized preventingdeflection of the cooling jets impinging at the leading edge.

The positioning structures (FIGS. 2 and 3) and 116 (FIG. 5) channelizethe flow of the cooling fluid along the concave side wall 71 and 104,respectively, in a manner to insure proper cooling thereon and toprohibit radial flow of the cooling air along the height of the vane, aswell as flow circulating between the concave side 71 and 104 and theconvex side 70 and 103.

What is disclosed then is a cooling system for a turbine vane structure,which cooling system effectively directs cooling air to the leadingedges 62 and 93 of the turbine vanes and 19, and, additionally, directscooling air to the convex side walls 65 and 103, of the vane structures.The apertures directing the cooling fluid to the sidewalls are inclinedrelative to the side walls and are circular to provide more jetpenetration and effective cooling of the convex side walls.Additionally, the trailing edges 68 and 101 are provided with expandibleseal structures 81 and 118 which effectively position the frames 58 and97 within the vane structures and also insures an even distribution andaccurate directional control of cooling air through the apertures in theleading edges 67 in 100 of the frames.

Although more than one embodiment has been shown, it is intended thatall the matter contained in the foregoing description and shown in theaccompanying drawings, shall be interpreted as illustrated and not in alimiting sense.

What is claimed is:

l. A vane structure for an elastic fluid axial flow machine, said vanestructure being generally of airfoil shape with leading and trailingedges and having a convex side and a concave side connecting said edges,said vane structure having an internal cavity defined by the internalsurfaces of said sides, a frame structure having leading and trailingedges connected by a convex side and a concave side, said frameconforming generally to the configuration of said cavity and beingdisposed in the cavity in spaced relation with the internal surfacesthereof to define coolant fluid passages extending from the leading edgeto the trailing edge of the vane between the corresponding sides of thevane and of the frame, said frame being open at one end to receivecoolant fluid and being closed at the other end, a first row ofapertures in the leading edge of the frame, the convex side of the framehaving at least one indented portion forming an elongated surfaceextending from one end to the other of the frame and being inclined atan acute angle with respect to the adjacent internal surface of thevane, a second row of apertures in said elongated surface, and dischargepassage means in the trailing edge of the vane for escape of the coolantfluid.

2. The structure of claim 1 and including means on the sides of theframe to direct the flow of coolant fluid from the leading edge to thetrailing edge of the vane.

3. The structure of claim 1 in which the frame structure has a sealingportion engaging one side of the vane adjacent the trailing edge, thesealing portion having a row of apertures therein adapted to equalizethe fluid pressures on opposite sides of the vane.

4. The structure of claim 3 and including means on the sides of theframe to direct the flow of coolant fluid from the leading edge to thetrailing edge of the vane.

1. A vane structure for an elastic fluid axial flow machine, said vanestructure being generally of airfoil shape with leading and trailingedges and having a convex side and a concave side connecting said edges,said vane structure having an internal cavity defined by the internalsurfaces of said sides, a frame structure having leading and trailingedges connected by a convex side and a concave side, said frameconforming generally to the configuration of said cavity and beingdisposed in the cavity in spaced relation with the internal surfacesthereof to define coolant fluid passages extending from the leading edgeto the trailing edge of the vane between the corresponding sides of thevane and of the frame, said frame being open at one end to receivecoolant fluid and being closed at the other end, a first row ofapertures in the leading edge of the frame, the convex side of the framehaving at least one indented portion forming an elongated surfaceextending from one end to the other of the frame and being inclined atan acute angle with respect to the adjacent internal surface of thevane, a second row of apertures in said elongated surface, and dischargepassage means in the traIling edge of the vane for escape of the coolantfluid.
 2. The structure of claim 1 and including means on the sides ofthe frame to direct the flow of coolant fluid from the leading edge tothe trailing edge of the vane.
 3. The structure of claim 1 in which theframe structure has a sealing portion engaging one side of the vaneadjacent the trailing edge, the sealing portion having a row ofapertures therein adapted to equalize the fluid pressures on oppositesides of the vane.
 4. The structure of claim 3 and including means onthe sides of the frame to direct the flow of coolant fluid from theleading edge to the trailing edge of the vane.